Re: [PATCH] perf callchain: Return directly when use '--call-graph dwarf' under !CONFIG_DWARF

[Tiezhu Yang]

On 12/14/2020 09:39 PM, Arnaldo Carvalho de Melo wrote:
> Em Mon, Dec 14, 2020 at 08:56:55PM +0800, Tiezhu Yang escreveu:
> > DWARF register mappings have not been defined for some architectures,
> > at least for mips, so we can print an error message and then return
> > directly when use '--call-graph dwarf'.
> >
> > E.g. without this patch:
> >
> > [root@linux perf]# ./perf record --call-graph dwarf cd
> > Error:
> > The sys_perf_event_open() syscall returned with 89 (Function not implemented) for event (cycles).
> > /bin/dmesg | grep -i perf may provide additional information.
> >
> > With this patch:
> >
> > [root@linux perf]# ./perf record --call-graph dwarf cd
> > DWARF is not supported for architecture mips64
> Good improvement on the message! But that .config-detected file isn't
> available at run time, take a look if this isn't a better alternative:

Hi Arnaldo,

Thank you very much, the following code with #ifdef HAVE_DWARF_SUPPORT
looks good and it works well on the x86 and mips arch.

So I will send a v2 patch as soon as possible.

Thanks,
Tiezhu

> diff --git a/tools/perf/util/callchain.c b/tools/perf/util/callchain.c
> index 1b60985690bba313..125178fd17482513 100644
> --- a/tools/perf/util/callchain.c
> +++ b/tools/perf/util/callchain.c
> @@ -276,6 +276,7 @@ int parse_callchain_record(const char *arg, struct callchain_param *param)
>   
>   		/* Dwarf style */
>   		} else if (!strncmp(name, "dwarf", sizeof("dwarf"))) {
> +#ifdef HAVE_DWARF_SUPPORT
>   			const unsigned long default_stack_dump_size = 8192;
>   
>   			ret = 0;
> @@ -290,6 +291,15 @@ int parse_callchain_record(const char *arg, struct callchain_param *param)
>   				ret = get_stack_size(tok, &size);
>   				param->dump_size = size;
>   			}
> +#else
> +			struct utsname uts;
> +
> +			ret = uname(&uts);
> +			pr_err("DWARF is not supported for architecture %s\n",
> +				ret ? "unknown" : uts.machine);
> +
> +			return -ENOTSUP;
> +#endif
>   		} else if (!strncmp(name, "lbr", sizeof("lbr"))) {
>   			if (!strtok_r(NULL, ",", &saveptr)) {
>   				param->record_mode = CALLCHAIN_LBR;
>
>   
> >   Usage: perf record [<options>] [<command>]
> >      or: perf record [<options>] -- <command> [<options>]
> >
> >          --call-graph <record_mode[,record_size]>
> >                            setup and enables call-graph (stack chain/backtrace):
> >
> > 				record_mode:	call graph recording mode (fp|dwarf|lbr)
> > 				record_size:	if record_mode is 'dwarf', max size of stack recording (<bytes>)
> > 						default: 8192 (bytes)
> >
> > 				Default: fp
> >
> > Signed-off-by: Tiezhu Yang <yangtiezhu@xxxxxxxxxxx>
> > ---
> >   tools/perf/util/callchain.c | 11 +++++++++++
> >   1 file changed, 11 insertions(+)
> >
> > diff --git a/tools/perf/util/callchain.c b/tools/perf/util/callchain.c
> > index 1b60985..a8cf456 100644
> > --- a/tools/perf/util/callchain.c
> > +++ b/tools/perf/util/callchain.c
> > @@ -18,6 +18,7 @@
> >   #include <math.h>
> >   #include <linux/string.h>
> >   #include <linux/zalloc.h>
> > +#include <sys/utsname.h>
> >   
> >   #include "asm/bug.h"
> >   
> > @@ -278,6 +279,16 @@ int parse_callchain_record(const char *arg, struct callchain_param *param)
> >   		} else if (!strncmp(name, "dwarf", sizeof("dwarf"))) {
> >   			const unsigned long default_stack_dump_size = 8192;
> >   
> > +			if (system("grep -q 'CONFIG_DWARF=y' .config-detected") != 0) {
> > +				struct utsname uts;
> > +
> > +				ret = uname(&uts);
> > +				pr_err("DWARF is not supported for architecture %s\n",
> > +					ret ? "unknown" : uts.machine);
> > +
> > +				return -ENOTSUP;
> > +			}
> > +
> >   			ret = 0;
> >   			param->record_mode = CALLCHAIN_DWARF;
> >   			param->dump_size = default_stack_dump_size;
> > --
> > 2.1.0